The present invention relates to a method for folding a medium. The present invention also relates to an apparatus equipped to execute the folding method as well as a printing system comprising an in-line combination of a print engine and the folding apparatus.
A method of this kind is known from European patent specification EP 0 379 712. This method executes a folding program, during which conveying rollers are driven in a feed direction to advance a web into a conveying pinch. The leading edge of the web is introduced into the pinch over its entire width by guide faces on guide rails. When the folding program is initiated a folding cylinder is driven in a first direction and in the opposite direction, depending on the required folds. When the folding cylinder is driven, the cylinder draws the web into the folder while the conveying pinch itself is freely rotatable in the feed direction but blocked in the reverse direction. When the direction of rotation is reversed, the blocking of the conveying pinch acts as a return stop and prevents the web from moving back. At the reversal of the cylinder's direction a bulge is formed. This bulge is guided into a fold pinch thereby forming a fold in the web. This procedure is repeated until the required folding configuration is reached.
A disadvantage of this known method is that it requires a complex construction with a return stop to prevent the paper web from moving back at the conveying pinch and a complex system of guide faces and guide means to guide the leading edge and formed bulges to form folds in the web. Another disadvantage of this known method and apparatus for executing such method is that the folding cylinder draws the web from the supply, which can put stresses on the web and even affect the integrity of the web.